package com.wuyong.chapter12;


import com.wuyong.chapter7.Map;

public class BSTMap<K extends Comparable<K>, V> implements Map<K, V> {

    private class Node {
        private K key;
        private V value;
        private Node left, right;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
        }
    }

    private int size;
    private Node root;

    public BSTMap() {
        root = null;
        size = 0;
    }

    @Override
    public void add(K k, V v) {
        root = add(root, k, v);
    }

    //向以node为根节点的二分搜索树中插入元素e， 递归算法
    //返回插入新节点后二分搜索树的根
    private Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }
        if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        }
        return node;
    }

    // 返回以node为根节点的二分搜索树中，key所在的节点
    private Node getNode(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (node.key.compareTo(key) > 0)
            return getNode(node.right, key);
        else if (node.key.compareTo(key) < 0)
            return getNode(node.left, key);
        else
            return node;
    }

    /**
     * 从二分搜索树中删除键为k的节点
     * @param k
     * @return
     */
    @Override
    public V remove(K k) {
        Node node = getNode(root, k);
        if (node != null) {
            root = remove(root, k);
            return node.value;
        }
        return null;
    }

    /**
     * 寻找最小值
     */
    public V getMinValue() {
        if (size == 0)
            throw new IllegalArgumentException("BST is empty!");
        return getMinValue(root).value;
    }

    private Node getMinValue(Node node) {
        if (node.left == null) {
            return node;
        }
        return getMinValue(node.left);
    }

    /**
     * 从二分搜索树种删除最小值所在节点，返回最小值
     *
     * @return
     */
    public V removeMin() {
        V ret = getMinValue();
        root = removeMin(root);
        return ret;
    }

    // 删除掉以node为根节点的二分搜索树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {
        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

    //Hibbard Deletion
    public Node remove(Node node, K key) {
        if (node == null)
            return null;

        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            return node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            return node;
        } else {   // key.compareTo(node.key) == 0

            // 待删除节点左子树为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }

            // 待删除节点右子树为空的情况
            if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }

            // 待删除节点左右子树均不为空的情况

            // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置
            Node successor = getMinValue(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;

            node.left = node.right = null;

            return successor;
        }
    }

    @Override
    public boolean contains(K k) {
        return getNode(root, k) != null ? true : false;
    }

    @Override
    public V get(K k) {
        Node node = getNode(root, k);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K k, V v) {
        Node node = getNode(root, k);
        if (node == null)
            throw new IllegalArgumentException(k + " doesn't exist!");

        node.value = v;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }
}
